The 9-mile-long lake on the Maquoketa River emptied in July 2010 when heavy rain caused the previous dam to fail.

Property owners formed a taxing district shortly after the storms, and voters approved a $6 million bond measure for the new dam and restoration. Other money came from the state, Delaware County and private donations.

Officials say the lake could refill in as little as a few days or take three or more weeks, depending on rainfall and river flow.